Method of forming fine patterns

ABSTRACT

Sidewalls of patterned resist are reformed using a reforming agent selected from the group consisting of (a) a carbon trichloride radical, (b) a mixture of silicon ion and oxygen ion, (c) a mixture of carbon ion and carbon monoxide ion, (d) a chlorine radical, (e) aluminum trichloride liquid and (f) dibutyl magnesium liquid, and sidewall reformed portions are thus formed on the sidewalls of pattern resist. The not reformed portion of the patterned resist is removed away, and sidewall reformed portions are left on an object layer. The portion of object layer excluding the portion immediately below sidewall reformed portions is etched away, and fine patterns of object layer are formed as a result.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods of forming finepatterns, and more particularly, to a method of forming patternsarranged in parallel with each other at very fine intervals and having avery fine width.

2. Description of the Background Art

FIGS. 38-41 are cross sectional views and perspective views showing asemiconductor device in each step in the order of a conventional methodof forming fine patterns. The fine patterns include interconnectionpatterns, bit lines, word lines etc.

Referring to FIG. 38, a layer of object to be patterned (hereinafterreferred to as object layer) 12 is formed on a support member 11 formedof a silicon dioxide film or the like. Object layer 12 is formed ofpolycrystalline silicon for example. Patterned resist 13 formed ofnovolak resin based positive photosensitive resin is formed on objectlayer 12.

Referring to FIG. 38 and 39, using patterned resist 13 as mask, objectlayer 12 is etched to remove the portion other than immediately belowpatterned resist 13 with a removing agent (such as bromine radical) 15for removing the object layer, and patterns 12A, 12B, 12C and 12D of theobject are formed.

Referring to FIGS. 40 and 41, patterned resist 13 is removed.

By the above-described method, patterns arranged in parallel to eachother at intervals D and having a width W are provided as illustrated inFIG. 41.

A problem associated with the above method will be now described.

The width (W) of patterns 12A, 12B, 12C or 12D of the object providedaccording to the conventional method is determined by the pattern widthof a light shielding film in the mask used (in the case of usingpositive photoresist) or the distance between light shielding films (inthe case of using negative photoresist). Therefore fine patterns havinga width and a size as small as or smaller than the minimum resolutionachieved by lithography cannot be formed. In other words, the patternwidth (W) and pattern distance (D) are each at least 0.25 μm, and finepatterns having pattern width (W) and distance (D) smaller than thissize cannot be formed.

FIGS. 42A-42F are cross sectional views showing a semiconductor devicein each step in the order of a method of forming fine patterns accordingto a prior art (Japanese Patent Laying-Open No. 2-5522) related to thepresent invention.

Referring to FIG. 42A, resist 2 is formed on a support member 1.

Referring to FIG. 42B, resist 2 is selectively irradiated with aultraviolet beam, and a latent image 3 is formed.

Referring to FIGS. 42B and 42C, developing resist 2 forms patternedresist 13.

Referring to FIG. 42D, a silylated layer 13a is formed on a surface ofpatterned resist 13 by irradiating support member 1 with a ultravioletbeam in vapor of hexamethyldisilazane (HMDS). Referring to FIGS. 42D and42E, silylated layer 13a formed on the top surface of patterned resist13 is removed by means of reactive ion etching.

Referring to FIGS. 42E and 42F, the not silylated portion of resist 13is etched away. Thus, fine patterns 16a are formed.

According to the conventional technique, however, a reaction chamber forreacting the photosensitive resin and HMDS must be improved such that afar ultraviolet beam can be introduced into the reaction chamber, whichcomplicates the device and pushes up the cost.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a method offorming patterns arranged in parallel with each other at fine intervalsand having a fine width.

Another object of the invention is to provide a method of forming finepatterns having a width and a distance smaller than a minimum resolutionachieved by lithography.

Yet another object of the invention is to provide a method of formingfine patters which can be implemented with a simple device.

In a method of forming fine patterns according to a first aspect of theinvention, an object layer is formed on a support member. Patternedresist having sidewalls opposite to each other is formed on the objectlayer. The one and the other sidewalls of the patterned resist arereformed using a reforming agent selected from the group consisting of(a) a carbon trichloride radical, (b) a mixture of silicon ion andoxygen ion, (c) a mixture of carbon ion and carbon monoxide ion, (d) achlorine radical, (e) aluminum trichloride liquid and (f) dibutylmagnesium liquid, whereby a first reformed portion on the sidewall(hereinafter simply referred to as first sidewall reformed portion) isformed on the one sidewall of the patterned resist, and a secondreformed portion on the sidewall (hereinafter referred to as secondsidewall reformed portion) on the other sidewall. The not reformedportion of the patterned resist is removed, and thus the first sidewallreformed portion and the second sidewall reformed portion are left onthe object layer. Using the first sidewall reformed portion and thesecond sidewall reformed portion as mask, the portion of the objectlayer excluding the portion immediately below the first and secondsidewall reformed portions are etched away, and thus fine patterns ofthe object are formed. The first sidewall reformed portion and thesecond sidewall reformed portions are then removed.

In a method of forming fine patterns according to a second aspect of theinvention, an object layer is formed on a support member. Patternedresist having sidewalls opposite to each other is formed on the objectlayer. The one sidewall and the other sidewall of the patterned resistare reformed, whereby a first sidewall reformed portion is formed on theone sidewall of the patterned resist and a second sidewall reformedportion is formed on the other sidewall. Using the patterned resistincluding the first and second sidewall reformed portions as mask, theportion of the object layer excluding the portion immediately below thepatterned resist is etched away, and patterns of the object are thusformed. The not reformed portion of the patterned resist is removed, andthus the first sidewall reformed portion and the second sidewallreformed portions are left on the patterns of the object. Using thefirst sidewall reformed portion and second sidewall reformed portion asmask, the portion of the object patterns excluding the portionimmediately below the first and second sidewall reformed portions isetched away, and even finer patterns of the object are formed as aresult. The first and second sidewall reformed portions are then removedaway.

In a method of forming fine patterns according to a third aspect of theinvention, an object layer is formed on a support member. Patternedresist having sidewalls opposite to each other is formed on the objectlayer. Using the patterned resist as mask, the portion of the objectlayer excluding the portion immediately below the patterned resist isetched away, whereby patterns of the object are formed and at the sametime the one and the other sidewalls of the patterned resist arereformed to form a first sidewall reformed portion on the one sidewallof the patterned resist and a second sidewall reformed portion on theother sidewall of patterned resist. The not reformed portion of thepatterned resist is removed away, and the first sidewall reformedportion and the second sidewall reformed portion are left on thepatterns of the object. Using the first and second sidewall reformedportions as mask, the portion of the patterns of the object excludingthe portion immediately below the first and second sidewall reformedportions is etched away, and even finer patterns of the object areformed as a result. The first and second sidewall reformed portions arethen removed away.

In a method of forming fine patterns according to a fourth aspect of theinvention, an object layer is formed on a support member. Patternedresist having sidewalls opposite to each other is formed on the objectlayer. Using the patterned resist as mask, the portion of the objectlayer excluding the portion immediately below the patterned resist isetched away, whereby patterns of the object are formed. The one and theother sidewalls of the patterned resist are reformed, and a firstsidewall reformed portion is formed on the one sidewall of the patternedresist and a second sidewall reformed portion is formed on the othersidewall of the patterned resist. The not reformed portion of thepatterned resist is removed, and the first and second sidewall reformedportions are thus left on the patterns of the object. Using the firstand second sidewall reformed portions as mask, the portion of thepatterns of the object excluding the portion immediately below the firstand second sidewall reformed portions is etched away, and even finerpatterns of the object are formed as a result. The first and secondsidewall reformed portions are then removed away.

By the method of forming fine patterns according to the first aspect ofthe invention, using the first and second sidewall reformed portionsformed on the sidewalls of the patterned resist as mask, the portion ofthe object excluding the portion immediately below the first and secondsidewall reformed portions is etched away. Fine patterns of the objectlayer are thus formed, and therefore patterns even finer than theminimum resolution achieved by the present lithography techniques can beprovided.

In addition, .the one and the other sidewalls of the patterned resistare reformed using as a reforming agent a carbon trichloride radical(CCl₃ ^(*)) which tends to dissociate with low energy, and thereforesidewall reformed portions containing a large amount of carbon can beformed on the sidewalls of the patterned resist.

Furthermore, implanting into the sidewalls of patterned resist as areforming agent two kinds of accelerated particles of (b) the mixture ofsilicon ion and oxygen ion, or (c) the mixture of carbon ion and carbonmonoxide ion causes a chemical change forming a new bond at the sidewallsurface of patterned resist, and a sidewall reformed portion havingproperties unremovable with a removing agent for etching away the objectlayer or a removing agent for removing the patterned resist can beformed.

Use of a chlorine radical (Cl₂ ^(*)) as a reforming agent can form asidewall reformed portion containing a large amount of carbon (C) with acarbon-carbon bond forming the patterned resist being cut.

If the patterned resist is soaked in aluminum trichloride liquid ordibutyl magnesium liquid, aluminum or magnesium atoms permeate into thesidewalls of the patterned resist and form oxide. The oxide is notremoved by the removing agent for etching away the object or theremoving agent for removing the patterned resist.

By the method of forming fine patterns according to the second aspect ofthe invention, using the first and second sidewall reformed portions asmask, the portion of patterns of the object excluding the portionimmediately below the first and second sidewall reformed portions isetched away, and therefore even finer patterns of the object can beformed.

By the method of forming fine patterns according to the third aspect ofthe invention, using the patterned resist as mask, the portion of theobject layer excluding the portion immediately below the patternedresist is etched away, whereby patterns of the object are formed atwhich time the one and the other sidewalls of the patterned resist arereformed, and therefore a first sidewall reformed portion is formed onthe one sidewall of the patterned resist and a second sidewall reformedportion on the other sidewall, and therefore the manufacturing processcan be simplified.

By the method of forming fine patterns according to the fourth aspect ofthe invention, using the patterned resist as mask, the portion of theobject layer excluding the portion immediately below the patternedresist is etched away, and the patterns of the object are thus formed.Thereafter, using the first and the second sidewall reformed portions asmask, the portion of the patterns of the object excluding the portionimmediately below the first and second sidewall reformed portions isetched away, and therefore even finer patterns of the object can beformed.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 6 are cross sectional views and perspective views showing asemiconductor device in first to sixth steps in the order of a method offorming fine patterns according to Embodiment 1;

FIGS. 7 to 13 are cross sectional views and perspective views showing asemiconductor device in first to seventh steps in the order of a methodof forming fine patterns according to Embodiment 2;

FIGS. 14 to 20 are cross sectional views and perspective views showing asemiconductor device in first to seventh steps in the order of a methodof forming fine patterns according to Embodiment 3;

FIGS. 21 to 28 are cross sectional views and perspective views showing asemiconductor device in first to eighth steps in the order of a methodof forming fine patterns according to Embodiment 4;

FIGS. 29A to 29F are cross sectional views showing a semiconductordevice in each step in the order of a method of forming fine patternsaccording to Embodiment 5;

FIGS. 30A to 30F are cross sectional views showing a semiconductordevice in each step in the order of a method of forming fine patternsaccording to Embodiment 6;

FIGS. 31A to 31E are cross sectional views showing a semiconductordevice in each step in the order of a method of forming fine patternsaccording to Embodiment 7;

FIG. 32 is a representation illustrating the concept of a plasma deviceused according to the present invention;

FIG. 33 is a representation illustrating the concept of an ashing deviceused according to the present invention;

FIGS. 34A to 34F are views showing a process preceding to a method offorming fine patterns according to Embodiment 17;

FIGS. 35A to 35D are perspective views showing a semiconductor device ineach step in the order of the method of forming fine patterns accordingto Embodiment 17;

FIGS. 36A to 36D are perspective views showing a semiconductor device ineach step in the order of a method of forming fine patterns according toEmbodiment 18;

FIGS. 37A to 37D are perspective views showing a semiconductor device ineach step in the order of a method of forming fine patterns according toEmbodiment 19;

FIGS. 38 to 41 are cross sectional views and perspective views showing asemiconductor device in first to fourth steps in the order of aconventional method of forming fine patterns; and

FIGS. 42A to 42F are cross sectional views showing a semiconductordevice in each step in the order of a conventional method of formingfine patterns according to a second conventional example related to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be now described in conjunction withthe accompanying drawings.

EMBODIMENT 1

FIGS. 1 to 6 are cross sectional views and perspective views showing asemiconductor device in each step in the order of a method of formingfine patterns according to Embodiment 1.

Referring to FIG. 1, an object layer 120 such as of polycrystallinesilicon is formed on a support member 110 of a silicon dioxide film orthe like. Resist patterns 130 of width W arranged parallel to each otherand having one sidewall 130a and the other sidewall 130b opposite toeach other are formed on object layer 120. Herein width W corresponds toa minimum resolution achieved by the present lithography techniques.

Referring to FIG. 2, as will be described later in detail, one sidewall130a and the other sidewall 130b of patterned resist 130 are reformedusing a reforming agent selected from the group consisting of (a) acarbon trichloride radical, (b) a mixture of silicon ion and oxygen ion,(c) a mixture of carbon ion and carbon monoxide ion, (d) a chlorineradical, (e) aluminum trichloride liquid and (f) dibutyl magnesiumliquid. By the reforming, a first sidewall reformed portion 132a isformed on one sidewall 130a of the patterned resist, and a secondsidewall reformed portion 132b is formed on the other sidewall 130b ofpatterned resist.

Referring to FIGS. 2 and 3, the portion of patterned resist 131 whichhas not been reformed is removed away, and thus first sidewall reformedportion 132a and second sidewall reformed portion 132b arranged inparallel to each other are left on object layer 120.

Referring to FIG. 3, 4, and 5, using first sidewall reformed portion132a and second sidewall reformed portion 132b as mask, the portion ofobject layer 120 excluding the position immediately below first andsecond sidewall reformed portions 132a and 132b is etched away with aremoving agent 150 for removing the object.

Referring to FIGS. 5 and 6, removal of first and second sidewallreformed portions 132a and 132b forms patterns 120A and 120B of theobject having a fine width w and a fine distance d smaller than theminimum resolution achieved by the present lithography are formed.

EMBODIMENT 2

FIGS. 7 to 13 are cross sectional views and perspective views showing asemiconductor device in each step in the order of a method of formingfine patterns according to Embodiment 2.

An object layer 120 is formed on a support member 110. Resist patterns130 arranged parallel to each other and having one sidewall and theother sidewall opposite to each other are formed on object layer 120.The one sidewall and the other sidewall of patterned resist 130 arereformed, and a first sidewall reformed portion 132a and a secondsidewall reformed portion 132b are thus formed on the one and the othersidewalls of the patterned resist.

Referring to FIGS. 8 and 9, using patterned resist 130 including firstsidewall reformed portion 132a and second sidewall reformed portion 132bas mask, the portion of object layer 120 excluding the portionimmediately below patterned resist 130 is etched away with a removingagent 150 for removing the object and patterns 125 of the object arethus formed.

Referring to FIGS. 9 and 10, the not reformed portion 131 of patternedresist is removed away, and first sidewall reformed portion 132a andsecond sidewall reformed portion 132b arranged parallel to each otherare left on the pattern 125 of the object.

Referring to FIGS. 11 and 12, using first and second sidewall reformedportion 132a and 132b as mask, the portion of patterns 125 of the objectexcluding the portion immediately below first and second sidewallreformed portions 132a and 132b is etched away with removing agent 150for removing the object.

Referring to FIGS. 12 and 13, removal of first and second sidewallreformed portions 132a and 132b forms patterns 120A and 120B of theobject having a fine width w and a fine distance d smaller than theminimum resolution achieved by the present lithography techniques.

EMBODIMENT 3

FIGS. 14 to 20 are cross sectional views showing a semiconductor devicein each step in the order of a method of forming fine patterns accordingto Embodiment 3.

Referring to FIG. 14, an object layer 120 is formed on a support member110. Patterned resist 130 arranged parallel to each other and having onesidewall 130a and the other sidewall 130b is formed on object layer 120.

Referring to FIGS. 15 and 16, using patterns 130 as mask, the portion ofobject layer 120 excluding the portion immediately below patternedresist 130 is etched away, patterns 125 of the object are thus formed,while reforming the one and the other sidewalls of each resist pattern,whereby a first sidewall reformed portion 132a is formed on one sidewallof resist pattern 130, and a second sidewall reformed portion 132b isformed on the other sidewall of resist pattern 130.

In the figures, reference numeral 142 represents a reforming andremoving agent capable of reforming the sidewalls of resist pattern 130and etching away the object layer.

Referring to FIGS. 16 and 17, the not reformed portion 131 of the resistpattern is removed away, and first sidewall reformed portion 132a andsecond sidewall reformed portion 132b arranged parallel to each otherare left on patterns 125 of the object.

Referring to FIGS. 18 and 19, using first and second sidewall reformedportions 132a and 132b as mask, the portion of patterns 120 of theobject excluding the portion immediately below first and second sidewallreformed portions 132a and 132b is etched away.

Referring to FIGS. 19 and 20, removal of first and second sidewallreformed portions 132a and 132b forms patterns 120A and 120B of theobject having a fine width w and a fine distance d smaller than theminimum resolution achieved by the present lithography techniques.

EMBODIMENT 4

FIGS. 21 to 28 are cross sectional views showing a device in each stepin the order of a method of forming fine patterns according toEmbodiment 4.

Referring to FIG. 21, an object layer 120 is formed on a support member110. Resist patterns 130 parallel to each other and having one sidewall130a and the other sidewall 130b opposite to each other are formed onobject layer 120.

Referring to FIGS. 22 and 23, using resist patterns 130 as mask, theportion of object layer 120 excluding the portion immediately belowresist patterns 130 is etched away with a removing agent 150 forremoving the object, and patterns 125 of the object are thus formed.

Referring to FIG. 24, the one sidewall and the other sidewall of resistpattern 130 are reformed, first sidewall reformed portion 132a is thusformed on the one sidewall of resist pattern and second sidewallreformed portion 132b is formed on the other sidewall of resist pattern.

Referring to FIGS. 24 and 25, the not reformed portion 131 of the resistpattern is removed away, and first sidewall reformed portion 132a andsecond sidewall reformed portion 132b arranged parallel to each otherare left on pattern 125 of the object.

Referring to FIGS. 26 and 27, using first and second sidewall reformedportions 132a and 132b as mask, the portion of patterns 125 of theobject excluding the portion immediately below first and second sidewallreformed portions 132a and 132b is etched away.

Referring to FIGS. 27 and 28, removal of first and second sidewallreformed portions 132a and 132b forms patterns 120A and 120B of theobject having a fine width w and a fine distance d smaller than theminimum resolution achieved by the present lithography techniques.

EMBODIMENT 5

FIGS. 29A to 29F are cross sectional views showing a semiconductordevice in each step in the order of a method of forming fine patternsaccording to Embodiment 5, and used for illustrating in more detail howthe sidewalls of the resist patterns according to Embodiment 1 arereformed.

Referring to FIG. 29A, an object layer 120 such as of a polysilicon(SiO₂) film is formed on a support member 110 for supporting the objectformed of silicon dioxide (SiO₂) film or the like. A resist pattern 130formed of novolak resin based positive photosensitive resin for exampleis formed on object layer 120.

Referring to FIG. 29B, a fixed amount of a reforming agent 140 of acarbon trichloride radical (CCl₃ ^(*)) is supplied on support member 110for a fixed time period.

Referring to FIG. 29C, carbon trichloride radical 140 sticks to thesurface of patterned resist 130 and the surface of object layer 120, andalso enters into patterned resist 130.

Referring to FIG. 29D, a removing agent 150 for removing the object suchas a bromine radical (Br^(*)) having directional dependance i.e.anisotropy is supplied onto support member 110. Since a carbontrichloride radical (CCl₃ ^(*)) which dissociates a carbon atom (C) withlow energy dissociates with the energy imparted by removing agent 150for removing the object, a thin carbon film is formed on the surface ofpatterned resist 130, and carbon atoms come into patterned resist 130from the surface to form sidewall reformed portion 132.

Referring to FIG. 29E, in the process of forming sidewall reformedportion 132, part of object layer 120, in other words part of thepolysilicon film forms a reaction product 730 such as silicontetrachloride (SICl₄) and silicon tetrabromide (SiBr₄) to be removed,and part of patterned resist 130 forms a reaction product 731 such acarbon tetrachloride (CCl₄) and carbon tetrabromide (CBr₄) to beremoved. Part of the carbon trichloride radical (CCl₃ ^(*)) returns toits ground state, and forms another reaction product, carbontetrachloride 732. These reaction products dissipate externally. Theupper end of patterned resist 130 has partially removed by the functionof removing agent 150 for removing the object.

Finally as illustrated in FIG. 29F, formed on a sidewall of thepatterned resist is a sidewall reformed portion 132 entered with acarbon thin film and/or carbon which cannot be completely removed withthe removing agent for removing the patterned resist such as an oxygenradical (O^(*)). Note that 131 represents the not reformed portion ofthe patterned resist.

The above carbon trichloride radical (CCl₃ ^(*)) is produced by acommonly used plasma device as illustrated in FIG. 32. The plasma deviceincludes a spare chamber CH71 and a reaction chamber CH72. In reactionchamber CH72, an electrode A(71) and an electrode B(72) are provided.Electrode B(72) also functions as a stand for an object. Gas G72 issupplied to electrode A(71) through a pressure regulator V72 and a flowrate regulator V72'. Gas G73 is supplied to electrode A(71) through apressure regulator V76 and a flow rate regulator V76'. Reaction chamberCH72 is connected to a turbo molecular pump TMP7 through valve V73.Turbo molecular pump TMP7 is connected to a rotary pump RP72. Sparechamber CH71 and reaction chamber CH72 are connected to each otherthrough a gate valve V74. Spare chamber CH71 is connected to a rotarypump RP71 through valve V71. Spare chamber 71 is supplied with gas G71.Gas 71 is supplied into spare chamber CH71 through a pressure regulatorV75 and a flow rate regulator V75'.

Reaction chamber CH72 is connected to an electromagnetic wave generatorRF through a coupling capacitor C.

A carbon trichloride radical (CCl₃ ^(*)) can be produced by supplying amixture gas of helium gas (G72) at a flow rate of 100 SCCM (StandardCubic Centimeter Per Minute) via pressure and flow rate regulators V72and V'72 and carbon tetrachloride gas (G73) at a flow rate in the rangefrom 60 to 80 SCCM via pressure and flow rate regulators V76 and V76',and then plasma-dissociating them under a pressure in the range from 1.0to 1.5 Torr.

Sidewall reformed portion 132 formed with reforming agent 140 of carbontrichloride radical (CCl₃ ^(*)) comes to have such a property that ER₀₁(the rate at which the not reformed portion 131 of the patterned resistis removed) is in the range from 100 to 140 nm/min, and ER_(O2) (therate at which sidewall reformed portion 132 is removed by the removingagent for removing the object) is in the range from 25 to 35 nm/min bythe function of removing agent 150 for removing the object such as abromine radical (Br^(*)).

Er₁₁ (the rate of removing the not reformed portion 131 of the patternedresist) given by the removing agent for removing the patterned resistsuch as an oxygen radical (O^(*)) was in the range from 115 to 135nm/min, and Er₁₂ (the rate of removing sidewall reformed portion 132)was in the range from 15 to 25 nm/min.

EMBODIMENT 6

Another example of the process of reforming sidewalls of the patternedresist according to Embodiment 1 will be described in the following.

In this embodiment, accelerated particles formed of two kinds of ionsare used as a reforming agent for forming such a sidewall reformedportion.

Referring to FIG. 30A, object layer 120 is formed on support member 110.Patterned resist 130 is formed on object layer 120.

Referring to FIG. 30B, a reforming agent 141 of accelerated particlesformed of two kinds of ions such as silicon ions (Si⁺) and oxygen ions(O⁺) or carbon ions (C⁺) and carbon monoxide ions (CO⁺) is supplied in afixed amount for a fixed time period toward sidewalls of patternedresist 130. Reforming agent 141 either reacts with patterned resist 130or enters into patterned resist 130, and a chemical change forming a newchemical bond such as Si-O and C-O occurs on the surface of patternedresist 130.

As a result, referring to FIG. 30C, sidewall reformed portion 132 whichhas changed as far as a prescribed depth forms on the surface ofpatterned resist 130. In the FIG. 131 represents the not reformedportion of the patterned resist.

Referring to FIG. 30D, a removing agent 150 for removing the object suchas a bromine radical (Br^(*)) having directional dependence i.e.anisotropy is supplied onto support member 110.

Referring to FIG. 30F, object layer 120, the polycrystalline siliconfilm for example forms into a reaction product A(730) of silicontetrabromide (SiBr₄), part of patterned resist 130 forms into a reactionproduct B(731) of carbon tetrabromide (CBr₄) for example, and part ofthe accelerated particles of reforming agent 141 which has come intopatterned resist 130 forms into a reaction product C(732) of silicontetrabromide (SiBr₄) or carbon tetrabromide (CBr₄). These reactionproducts dissipate externally. Supplying removing agent 150 for removingthe object in a fixed amount for a fixed time period forms sidewallreformed portion 130 containing chemical bonds of silicon (Si) andcarbon (C) which cannot be completely removed with removing agent 150for removing the object or the removing agent for removing the notreformed portion 131 of the patterned resist.

The accelerated particles of reforming agent 141 can be produced with acommonly used ion implantation device. Accelerated particles can bedirected obliquely toward patterned resist 130 by changing the angle atwhich the accelerated particles are irradiated. The depth to which theaccelerated particles come into patterned resist 130 is determined bychanging easily controllable ion energy. Therefore, the width (w) ofsidewall reformed portion 132 can be readily controlled. For example forsilicon ions (Si⁺) and oxygen ions (CO⁺) with an implantation energy of50 keV in a dose of 10¹⁶ atoms/cm², the depths of the highest portionsof the concentration of the implanted ions are 115 nm and 70 nm, andsidewall reformed portion 132 having a width corresponding to the depthsis formed. ER₀₁ by the removing agent for removing the object such as abromine radical (Br^(*)) is in the range from 50 to 70 nm/min, and ERO₂is in the range from 15 to 25 nm/min. The removing agent for removingthe patterned resist such as an oxygen radical (O^(*)) was in the rangefrom 115 to 135 nm/min and ER₁₂ was in the range from 5 to 10 nm/min.

EMBODIMENT 7

FIGS. 31A to 31E are schematic representations for use in illustrationof a process of reforming sidewalls of patterned resist in Embodiment 7.

In this embodiment, a chlorine radical (Cl₂ ^(*)) capable of forming asidewall reformed portion on the sidewall of patterned resist and ofremoving an object layer as well is used as a reforming agent.

Referring to FIG. 31A, an object layer 120 is formed on a support member110. Patterned resist 130 is formed on object layer 120.

Referring to FIG. 31B, a fixed amount of a chlorine radical (Cl₂ ^(*)),a reforming and removing agent 142 having directional dependence i.e.anisotropy is supplied onto support member 110 for a fixed time period.

Referring to FIG. 31C, the chlorine radical (Cl₂ ^(*)) reacts withobject layer 120 in other words polycrystalline silicon and forms into areaction product A(730) of silicon tetrachloride (SiCl₄). Part ofpatterned resist 130 forms into a reaction product B(731) such as carbontetrachloride (CCl₄). Part of the chlorine radical (Cl₂ ^(*)) returns toits ground state, and forms into another reaction product C(732),chlorine. These reaction products dissipate externally as illustrated inFIG. 31C. Although part of the surface of patterned resist 130dissipates in the form of reaction product B(731), since a chlorineradical (Cl₂ ^(*)) is more active than a carbon trichloride radical(CCl₃ ^(*)), the bond (-C-) of patterned resist 130 is cut off, andsidewall reformed portion 132 containing a large amount of carbon (C)forms on the side surface of patterned resist 130. Most of chlorineradicals (Cl₂ ^(*)) sticking onto the surface of object layer 120 reactwith object layer 120, and dissipate externally in the form reactionproduct A(730) as illustrated in FIG. 31D, and thus function to removeobject layer 120. As a result, supply of a fixed amount of chlorineradical (Cl₂ ^(*)) for a fixed time period removes object layer 120, andfinally sidewall reformed portion 132 entered with a carbon thin filmand/or carbon which cannot be completely removed with a removing agent(such as oxygen radical (O^(*))) for removing the not reformed portionof the patterned resist is formed on a sidewall of patterned resist 130as illustrated in FIG. 31E.

The chlorine radical (Cl₂ ^(*)) can be produced with a commonly usedplasma device as illustrated in FIG. 32. More specifically, a mixturegas of helium gas (G72) at a flow rate of 100SCCM through pressure andflow rate regulators V72 and V'72 and chlorine gas (G72) at a flow rateof 100 SCCM through pressure and flow rate regulators V76 and V'76 issubjected to plasma-dissociation between electrode A(71) and electrodeB(72) under a pressure of 250 mTorr. A generated reaction product is letout with helium gas (G72). If the temperature of a station (72) for anobject is in the range from 50° to 60° C., a radio wave power is in therange from 220 to 260 W, and the distance between electrode A(73) andobject (120) is 1.1 cm, object 120 is removed at such a rate at whichER₂₀ (the rate of removing the object with reforming and removing agent142) is in the range from 450 to 500 nm/min, and sidewall reformedportion 132 having a width in the range from 0.15 to 0.25 μm forms. ER₄₁(the rate at which the not reformed portion 131 of the patterned resistis removed with reforming and removing agent 142) is in the range from220 to 260 nm/min, ER₄₂ (the rate at which sidewall reformed portion 132is removed with reforming and removing agent 142) is in the range from60 to 80 nm/min, and ER₄₃ (the rate at which the support member forsupporting the object is removed with reforming and removing agent 142)is in the range from 15 to 20 nm/min.

Reforming and removing agent 142 or removing agent 150 for removing theobject described above is formed with a commonly used plasma device asillustrated in FIG. 32. FIG. 33 is a representation showing thearrangement of an ashing device for generating a removing agent forremoving the not reformed portion of the patterned resist.

In FIG. 33, CH82 is a reaction chamber, and CH81 is a spare chamber forkeeping an object for a while. RP81 and V81 are a rotary pump and avalve for exhausting spare chamber CH81. Gas 81 such as nitrogen isintroduced into spare chamber CH81 through pressure and flow rateregulars V85 and V'85, and the chamber is exhausted by rotary pump RP81.After repeating introduction/exhaustion of the nitrogen gas, sparechamber CH81 is brought into a vacuum of 10⁻² Torr, in which an objectto be processed is kept. Reaction chamber CH82 installed with the objectis brought into a vacuum of 10⁻⁴ Torr by a turbo molecular pump TMP8 anda rotary pump RP82, and the residual gas is let out. In the figure (MW)represents an electromagnetic wave generator. (80) is a microwavegenerated by electromagnetic wave generator (MW), and (81) is awaveguide. (82) is a teflon plate for matching waveguide 81 and reactionchamber CH82. An alumina (Al₂ O₃) window plate 83 partitions the spacebetween waveguide 81 and reaction chamber CH82, and introduces microwave80 from waveguide 81 into reaction chamber CH82. Reaction chamber CH82is provided with a shower head 84. Reactive particles to function as aremoving agent for removing the patterned resist is blown from showerhead 84. Support member 110 is placed on a station 86 for an object.

An oxygen radical (O^(*)), an example of such a removing agent forremoving the patterned resist is produced as follows as illustrated inFIG. 33. A microwave 80 at 2.45 GHz generated by electromagnetic wavegenerator (MW) is introduced into reaction chamber CH82 throughwaveguide 81. Dissociating oxygen O₂ gas (G83) under a pressure in therange from 1 to 2 Torr at a flow rate of 1000 SCCM through pressure andflow rate regulators V86 and V'86 provides an oxygen radical (O^(*)). Ifthe temperature of object station 86 is in the range from 100° to 200°C., the microwave power is in the range from 400 to 1500 W, and thedistance between the shower head from which oxygen radical 85 isdischarged and the not reformed portion 131 of patterned resist is inthe range from 5 to 6 cm, the not reformed portion 131 of patternedresist is removed away at a removing rate in the range from 1 to 2μm/min.

EMBODIMENT 8

In this embodiment, aluminum trichloride (AlCl₃) liquid or dibutylmagnesium [Mg(Bu)₂ ] liquid is used as a reforming agent. For aluminum,aluminum trichloride (Alcl₃) liquid is used. The aluminum trichlorideliquid is produced by dissolving 1.8 mol/l aluminum trichloride into asolvent of nitrobenzene. For magnesium, dibutyl magnesium liquid ordiethyl magnesium liquid is used. Dibuthyl magnesium liquid is producedby dissolving 0.7 mol/l dibutyl magnesium in a solvent of heptane. Thediethyl magnesium liquid is produced by dissolving 0.7 mol/l diethylmagnesium in a solvent of diethylether. The support member with thepatterned resist formed thereon is soaked in the dibutyl magnesiumliquid or diethyl magnesium liquid for one minute and then washed withtoluene and then hexane. Then, drying is conducted by blowing nitrogengas. The series of treatments are all conducted in nitrogen gas. Throughthese treatments, referring to FIG. 1, for example, metal atoms ofaluminum or magnesium come into the surface of patterned resist 130 fromits surface. These metals are oxidized with oxygen present in patternedresist 130 and form an inorganic substance. The inorganic substance andan organic substance of the patterned resist in the form of a matrixform sidewall reformed portions 132a and 132b. Sidewall reformedportions 132a and 132b are formed to have such a property that they arenot removed with a removing agent for removing the object or a removingagent for removing the patterned resist.

Sidewall reformed portions 132a and 132b treated with dibutyl magnesiumliquid exhibit the following property. For example, ER₀₁ (the rate atwhich the not reformed portion 131 of patterned resist is removedsecondarily by the removing agent for removing the object) with removingagent 150 for removing the object is in the range from 50 to 70 nm/min,and ER₀₂ (the rate at which sidewall reformed portions 132a and 132b areremoved with removing agent 150 for removing the object) is in the rangefrom 5 to 15 nm/min.

In addition, ER₁₁ (the rate at which the not reformed portion 131 ofpatterned resist is removed with the removing agent for removingpatterned resist) with the removing agent for removing the patternedresist is in the range from 115 to 135 nm/min, and ER₁₂ (the rate atwhich sidewall reformed portions 132a and 132b are removed with theremoving agent for removing the patterned resist) is in the range from 5to 15 nm/min.

In this embodiment, the patterned resist is soaked in aluminumtrichloride liquid or dibutyl magnesium liquid, and the liquid is madeto permeate into the surface of the patterned resist and thus sidewallreformed portions 132a and 132b are formed. The width (w) of sidewallreformed portions 132a and 132b can be controlled based on time forsoaking.

As a removing agent for removing a sidewall reformed portion, ahydrofluoric acid aqueous solution or a buffer hydrofluoric acid aqueoussolution is used. The hydrofluoric acid aqueous solution used has avolume ratio of water and hydrofluoric acid (HF content: 50%) of10-50:1. The buffer hydrofluoric acid aqueous solution used has a volumeratio of ammonium fluoride (NH₄ F content: 40%) and hydrofluoric acid of5-10:1. Removal of a sidewall reformed portion with the removing agentfor removing the sidewall reformed portion also has a mechanism ofremoving by the function of a so-called lift off effect, and theremoving rate ER₂₂ (the rate at which sidewall reformed portions 132aand 132b are removed with the removing agent for removing the sidewallreformed portions) is 5 to 6 seconds. For the removing time, ER₂₀ (therate at which object 120 is removed with the removing agent for removingsidewall reformed portion) and ER₂₃ (the rate at which support member110 is removed with the removing agent for removing sidewall reformedportion) are very small.

EMBODIMENT 9

In this embodiment, a carbon trichloride radical and a mixture ofsilicon ion and oxygen ion are selected as a reforming agent for forminga sidewall reformed portion. Using the carbon trichloride radical, oneand the other sidewalls of patterned resist are reformed. Then, usingthe mixture of silicon ion and oxygen ion, one and the other sidewallsof patterned resist are once again reformed. By such a method, theadvantages of both (by the first reforming treatment and the secondreforming treatment) are exhibited, and high performance sidewallreformed portions are formed.

EMBODIMENT 10

In this embodiment, a carbon trichloride radical and a mixture of carbonion and carbon monoxide ion are selected as reforming agents for formingsidewall reformed portions. One and the other sidewalls of patternedresist are reformed with the carbon trichloride radical. Then, using themixture of carbon ion and carbon monoxide ion, the one and the othersidewalls of patterned resist are once again reformed. By such a method,both advantages are synergistically exhibited, and sidewall reformedportions with excellent performance are provided.

EMBODIMENT 11

In this embodiment, a chlorine radical and a mixture of silicon ion andoxygen ion are selected as reforming agents for forming sidewallreformed portions. With the chlorine radical, one and other sidewalls ofpatterned resist are reformed. Then, with the mixture of silicon ion andoxygen ion, the one and the other sidewalls of patterned resist are onceagain reformed. By such a method, both advantages are synergisticallyexhibited, and sidewall reformed portions obtained will give excellentperformance.

EMBODIMENT 12

In this embodiment, a chlorine radical and a mixture of carbon ion andcarbon monoxide ion are selected as reforming agents for formingsidewall reformed portions. With the chlorine radical, one and the othersidewalls of patterned resist are reformed. Then, with the mixture ofcarbon ion and carbon monoxide ion, the one and the other sidewalls ofpatterned resist are once again reformed. By such a method, bothadvantages are synergistically exhibited, and sidewall reformed portionsobtained will give excellent performance.

EMBODIMENT 13

In this embodiment, aluminum trichloride liquid and a mixture of siliconion and oxygen ion are selected as reforming agents for forming sidewallreformed portions. Using the aluminum trichloride liquid, one and theother sidewalls of patterned resist are reformed. Then, with the mixtureof silicon ion and oxygen ion, the one and the other sidewalls ofpatterned resist are once again reformed. By such a method, bothadvantages are synergistically exhibited and the sidewall reformedportions obtained will have excellent performance.

EMBODIMENT 14

In this embodiment, aluminum trichloride liquid and (c) a mixture ofcarbon ion and carbon monoxide ion are selected as reforming agents forforming sidewall reformed portions. One and the other sidewalls ofpatterned resist are reformed using the aluminum trichloride liquid.Then, with the mixture of carbon ion and carbon monoxide ion, the oneand the other sidewalls of patterned resist are once again reformed. Bysuch a method, both advantages are synergistically exhibited, andsidewall reformed portions obtained will give excellent performance.

EMBODIMENT 15

In this embodiment, (f) dibutyl magnesium liquid, and (b) a mixture ofsilicon ion and oxygen ion are selected as reforming agents for formingsidewall reformed portions. Using the dibutyl magnesium liquid, one andthe other sidewalls of patterned resist are reformed. Then, with themixture of silicon ion and oxygen ion, the one and the other sidewallsof patterned resist are once again reformed. By such a method, bothadvantages are synergistically exhibited, and sidewall reformed portionsformed will give excellent performance.

EMBODIMENT 16

In this embodiment, (f) a dibutyl magnesium liquid and (c) a mixture ofcarbon ion and carbon monoxide ion are selected as reforming agents forforming sidewall reformed portions. Using the dibutyl magnesium liquid,one and the other sidewalls of patterned resist are reformed. Then, withthe mixture of carbon ion and carbon monoxide ion, the one and the othersidewalls of patterned resist are once again reformed. By such a method,both advantages are synergistically exhibited, and sidewall reformedportions formed will give excellent performance.

EMBODIMENT 17

This embodiment relates to a method of further working fine patternsobtained according to the above-described methods.

Referring to FIG. 34A, an object layer 120 is formed on a support member110. Patterned resist 130 is formed on object layer 120.

Referring to FIG. 34B, A sidewall of patterned resist 130 is reformedand a sidewall reformed portion 132 is formed. Using patterned resist130 including sidewall reformed portion 132 as mask, the portion ofobject layer 120 excluding the portion immediately below patternedresist 130 is etched away, and a pattern 125 of the object is thusformed.

Referring to FIGS. 34C and 34D, the not reformed portion 131 ofpatterned resist 130 is removed away, and sidewall reformed portion 132is left on pattern 125 of the object.

Referring to FIG. 34E, using sidewall reformed portion 132 as mask, theportion of pattern 125 of the object excluding the portion immediatelybelow sidewall reformed portion 132 is etched away.

Referring to FIG. 34F, by removal of the sidewall reformed portion, apair of fine patterns 120A and 120B parallel to each other, and a pairof fine patterns 120C and 120D linking ends of the pair of fine patterns120A and 120B are formed.

FIG. 35A corresponds to FIG. 34F.

Referring to FIG. 35B, in order to expose pair of fine patterns 120C and120D, resist 130 is applied on pattern 120 of the object.

Referring to FIGS. 35B and 35C, using resist 130 as mask, pair of finepatterns 120C and 120D are etched away. Then, removal of resist 130provides a pair of fine patterns 120A and 120B arranged parallel to eachother as illustrated in FIG. 35D.

EMBODIMENT 18

FIG. 36A and 36D are perspective views showing a method of forming finepatterns according to Embodiment 18. FIG. 36A corresponds to FIG. 34F.

Referring to FIGS. 36A and 36B, resist 130 is formed on fine pattern 120so as to expose only one fine pattern 120D of pair of fine patterns 120Cand 120D arranged parallel to each other.

Referring to FIG. 36C, using resist 130 as mask, the one fine pattern120D is etched away.

Referring to FIGS. 36C and 36D, removal of patterned resist 130 forms apair of fine patterns 120A and 120B arranged parallel to each other anda fine pattern 120C linking their ends.

EMBODIMENT 19

FIGS. 37A to 37D are perspective views showing a method of forming finepatterns according to Embodiment 19.

FIG. 37A corresponds to FIG. 34F.

Referring to FIG. 37B, resist 130 is formed on a support member 110 soas to expose fine pattern 120B, part of fine pattern 120C, and part offine pattern 120D. Referring to FIGS. 37B and 37C, using patternedresist 130 as mask, fine pattern 120B, part of fine pattern 120C andpart of fine pattern 120D are etched away. Resist 130 is then removedaway.

Referring to FIG. 37D, a fine pattern formed of fine pattern 120A, partof fine pattern 120C and part of fine pattern 120D is formed.

By the method of forming fine patterns according to the first aspect ofthe invention, using first and second sidewall reformed portions formedon sidewalls of patterned resist as mask, the portion of the objectlayer excluding the portion immediately below the first and secondsidewall reformed portions are etched away, and fine patterns of theobject layer are thus formed. As a result, patterns even finer than theminimum resolution achieved by the present lithography techniques areprovided.

By the method of forming fine patterns according to the second aspect ofthe invention, using first and second sidewall reformed portions asmask, the portion of patterns of the object excluding the portionimmediately below the first and second sidewall reformed portions isetched away, and therefore even finer patterns of the object can beformed. As a result, patterns finer than the minimum resolution achievedby the present lithography techniques can be advantageously provided.

By the method of forming fine patterns according to the third aspect ofthe invention, using patterned resist as mask, the portion of the objectlayer excluding the portion immediately below the patterned resist isetched away, patterns of the object are thus formed, while reforming oneand the other sidewalls of the patterned resist, thus a first sidewallreformed portion is formed on the one sidewall of patterned resist and asecond sidewall reformed portion on the other sidewall of patternedresist, and therefore the manufacturing process is simplified.

By the method of forming fine patterns according to the fourth aspect ofthe invention, using patterned resist as mask, the portion of the objectlayer excluding the portion immediately below the patterned resist isetched away, and thus patterns of the object are formed. Then, using thefirst and second sidewall reformed portions as mask, the portion of thepatterns of the object excluding the portion immediately below the firstand second sidewall reformed portions is etched away, and therefore evenfiner patterns of the object can be formed. As a result, patterns evenfiner than the minimum resolution achieved by the present lithographytechniques can advantageously be provided.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A method of forming a fine pattern, comprisingthe steps of:forming an object layer on a support member; forming onsaid object layer patterned resist having opposing side surfaces;converting a portion of the patterned resist on each opposing sidesurface to form first and second opposing sidewalls leaving unconvertedresist therebetween, wherein said first and second sidewalls exhibitetch characteristics different from said unconverted resist; etchingaway the portion of said object layer excluding the portion immediatelybelow said patterned resist, using as mask said patterned resistincluding said first and second sidewalls, thereby forming a pattern ofthe object; removing the unconverted part of said patterned resist,thereby leaving said first and second sidewalls on said pattern of theobject; etching away the portion of said pattern of the object,excluding the portion immediately below said first and second sidewalls,using said first and said second sidewalls as a mask, thereby forming afiner pattern of said object; and removing said first and secondsidewalls.
 2. The method according to claim 1, whereinsaid first andsecond sidewalls are converted using an agent selected from the groupconsisting of a carbon trichloride radical, (b) a mixture of silicon ionand oxygen ion, (c) a mixture of carbon ion and carbon monoxide ion, (d)a chlorine radical, (e) aluminum trichloride liquid and (f) dibutylmagnesium liquid.